In the practice of orthodontics sometimes molars on one side of the patient's mouth move faster than molars on the other side. At other times molars on one side may be in the proper position at the beginning of treatment. In either case the orthodontist wants to apply force only to the molars which need to be moved.
Many facebow designs have been used to try to eliminate applying force to a properly positioned molar. One known technique is to use a swivel near the distal end of the inner bow on the side next to the molars which are in the proper position. The resulting facebow is called a unilateral facebow since it applies force mainly on one side. The side on which the molars are in the proper position is called the non-force side. The purpose of the swivel is to reduce or eliminate the transmission of force to the molars on the non-force side to reduce or eliminate their displacement during treatment.
The prior art method used by the orthodontist to fashion the force breaking swivel typically proceeds as follows. First the orthodontist bends the distal end of the non-force inner bow downwardly at about a 90.degree. angle. Using a small hand-grinder, flats are ground on the lateral sides of the downwardly extending distal end. A length of tubing is scored with a triangular file so that it can be fractured and broken off at the proper length. The end of the tubing is then bent over to partially fracture it at the score mark. Using the still attached main portion of the tubing as a handle, the end of a thin foil strip, having a width about equal to the length of the tube segment, is soldered to the outside of the tube segment. The foil strip is then trimmed to be about as long as it is wide.
This foil strip is then wrapped around the downwardly extending bent distal end of the inner bow and is soldered to it. Care must be taken to assure that the tube segment does not become filled with solder and that it is properly positioned. The main portion of the tubing is usually broken away from the tube segment before the last mentioned soldering step. The distal end of the inner bow, with the tube segment attached, is smoothed to remove the rough edges and is then buffed.
The end of a length of wire is then bent into an L-shape. The main length of the wire is passed through the top of the tube segment until the corner bend is reached. The main length of wire is then bent back over to form a semi-circular curve to keep the generally L-shaped swivel member from falling out of the tube segment. Finally, the main length of the wire is cut to the desired length and the cut end is filed and smoothed.
The main drawback with this prior art method is that it takes a relatively experienced practitioner from 10 to 20 minutes to fashion such a swivel. In addition some orthodontists may not use a force breaking swivel because of their lack of familiarity with the above fabrication procedure.